Automatic thickness regulator for strip rolling mills



June 1, 1965 H. s. MAXWELL 3,186,200

AUTOMATIC THICKNESS REGULATOR FOR STRIP ROLLING MILLS Filed Oct. 51, 1961 5 sneets-sheetl FIG.II

HUGH S.MAXWELL ATTORNEY INVENTOR.

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AUTOMATIC THICKNESS REGULATOR FOR STRIP ROLLING MILLS Filed Oct. 51. 1961 5 Sheets-Sheet'3 FIG.3

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INVENTOR.

HUGH S. MAXWELL ATTORNEY United States Patent O 3,186,200 AUTOMATIC THICKNESS REGULATOR FDR STRlP ROLLING MILLS Hugh S. Maxwell, Schenectady, N.Y., assignor to General Electric Company, a corporation of New York Filed (lot. 31, 1961, Ser. No. 149,086 Claims. (Cl. 728) My invention relates to means for use in rolling mills in which strips of material are rolled in successive, or tandem, roll stands, under pressure applied by the stands, to reduce the thickness of the strips to a desired thickness. Such mills are used, for example, in the steel industry in producing thin strips, or sheets, of steel.

My invention has for one of its objects to provide means automatically to regulate the pressure applied by the mill stands during the rolling of strip material in accord with any deviations in thickness of the strip previously rolled from desired value thereby to reduce the deviation in thickness from the desired value in the rolling of the succeeding strip.

A further object of my invention is to provide means to measure the deviation in the thickness of each strip rolled and to produce a parameter representative of the average deviation of such thickness from the desired value, and to utilize that parameter automatically to adjust the pressure applied by the stand rolls to the next strip rolled.

The reduction in the thickness of the strip produced by any mill stand, however, is dependent not only on the pressure applied to the material by the rolls of the stands, but also by the tension to which the strip is subjected while in the stands. This is particularly true when rolling hot material, for example, hot steel strip. This tension may be produced, not only by the operation of the thickness reducing roll stands, but by tension generated by operation of the reels, or other equipment, on which the strip is stored as it leaves the mill, or by equipment from which the strip is supplied as it enters the mill. The .end portions of the strip, therefore, that is the forward end as it enters the mill and, particularly, before all stands are occupied, and the tail end after it leaves the first stand of the mill, are not subject to tension that is accurately representative of the condition during the rolling of the balance of the strip. Accordingly, a further .object of my invention is to exclude these end portions from any effect upon the adjustment of the pressure during the rolling of the next strip.

A further object of my invention is to effect the adjustment of pressure to be applied by any stand at a time When the stand is not occupied by a strip, that is, at a time between strips, and to preserve that adjustment during the rolling of the subsequent strip. Since the strips may follow each other through the mill with very close spacing, sometimes less than the interval between adjacent stands, a further object of my invention is to eliect the adjustment of the different stands in succession, each stand being adjusted immediately after the tail end of the strip leaves the stand, and before the next strip enters the stand.

In carrying my invention into etfect, and in accord with the embodiment presently to be described, any desired means are employed tomeasure the thickness of the strips as they leave the mill. This means preferably includes means for producing an error voltage of direction and magnitude varying in accord with the direction and .magnitude of any deviation from desired value of the thickness of the strip being measured. This voltage is integrated during only the interval in the rolling of the respective strip when all of the stands are occupied by a single strip, thereby excluding the end portions which are not under normal rolling tension. The integrated voltage is supplied to an average computer, which may comprise a potentiometer, having a variable contact which is movedalong the potentiometer from the high potential end toward the other at uniform rate during the same interval, the potentiometer being so proportioned that the potential of said contact comprises a parameter representative of the average thickness of the strip over the length passing the measuring device during the interval.

At the end of the interval, throughrelay action, this voltage is supplied to servo positioning device which is positioned and provided to supply appropriate voltage to the roll pressure adjusting mechanism of the various stands in succession as the tail end of the strip measured leaves the respective stands. Simultaneously said integrated voltage is discharged, or terminated, and the potentiometer contact returned to its starting position in readiness for the next integrating interval.

.In this way each stand is adjusted between strips in accord with said parameter to produce pressure during rolling of the next strip to effect more nearly the desired dimension in the rolling of the next strip. 7

A second servo positioning device responds to the position of the first device and acts as a storage, or memory, of said parameter during the interval when the next strip occupies all stands. This positioning device is utilized, through relay action, to supply to the different pressure adjusting means voltage corresponding in character to this voltage supplied thereto by the first positioning device at the end of the last integrating interval thereby to maintain said adjustment during the instant interval.

This operation is repeated for each strip rolled.

By use of my invention it is contemplated that the number of stands required to be equipped with automatic pressure adjustment means may be reduced thereby reducing the total cost of the equipment while at the same time attaining improved thickness control of the strips The novel features which I believe to be characteristic of my invention are set forth with particularity in the appended claims. My invention itself, however, both as toits organization and method of operation, together with further objects and advantages thereof, may best be understood by reference to the following description taken in connection with the accompanying drawings in which FIGS. 1, 2, 3, 4 and 5, taken together in the relationship illustrated in FIG. 6, with lines which extend from one figure to another in alignment, illustrate a single embodiment of the invention.

Referring to the drawings, I have shown, by way of example, at 1, 2, 3, 4, 5 and 6, six stands of a steel rolling mill. As illustrated, each of these stands may comprise a pair of rollers 7, one in each stand above the strip of steel 8 being rolled, and the other below, and between which the strip passes during the rolling operation. These rollers 7 are each driven in any suitable way, but as illustrated are each driven by motors 9 through driving connections illustrated by dotted lines 10.

Each stand also comprises back up rollers 13 and '14, usually of considerably larger diameter than the rollers 7, but which engage the rollers 7 to bring desired pressure upon the strip of steel 8 being rolled.

In addition, each stand comprises a suitable frame, or housing, not shown in the drawings, in which the rollers are supported, and which include bearings, represented by the circles 15 and 16, and stationary members 17 provided with a so-called screwdown 18. This screwdown bears upon the bearing 15 and is provided at its upper end with a splined shaft portion 19 extending through the splined aperture in a gear 22, so that it may move up or down in response to rotation of the gear to bring desired pressure on the bearing 15 and hence on the rollers 7 and the strip 8. This gear is driven by a worm 23, which is operated through a suitable worm drive 24 up or down.

These motors 25 are each operated by a suitable control mechanism represented by rectangles S to S respectively, to bring desired pressure by means of the screwdown 18 on to the bearing 15 to etfect the desired degree of diminution in dimension of the steel strip as it passes the stand.

These control systems S to S may be of any desired type such as those of the continuous type illustrated in Patents 2,726,541 Sims, and 2,680,978 Hesscnberg, or of the program type, such as that described in Kelling et al. Patent No. 2,848,670. Both types may be employed on some stands and one or the other on other stands.

I particularly contemplate my invention as means to apply a corrective factor to systems of either of these types, or of other types, this corrective factor varying with, and in a direction to counteract, undesired variations in the thickness of the strip as it leaves the mill. Of course, it may also be employed as the sole means for automatically compensating for undesired variations in thickness of the strip as it comes from the mill.

In accord with the presently to be described embodiment of my invention, this corrective factor is represented by a correction signal that comprises an alternating electromotive force supplied through transformers T to T and associated potentiometers to the equipments S to S to adjust the screwdown to compensate for variations in strip thickness and to maintain desired thickness of the successive strips as they come from the mill. The potentiometers permit adjustment of the individual stands with any preselected portion of the correction signal. If the systems of the above-referred to Kelling et al. patent be employed, for example, this alternating electromotive force may be applied to the input of discharge device 49a, illustrated in that patent, in series, and in proper phase with the electromotive force present in that system.

The above-mentioned Sims patent describes a thickness control system which operates according to the law where h is the roll strip thickness, F is the roll separating force, M is the elastic constant, or spring, of the mill, and So is the roll setting. Where my invention is applied to such a system the equation would become where D represents the corrective factor generated by my invention.

While in the specific embodiment to be described herein the correction factor voltage supplied to the equipments S is an alternating voltage of one phase or of opposite phase and of magnitude to effect the desired thickness compensation through the equipments S, it will be understood that this voltage may be unidirectional and of polarity and magnitude to effect the desired compensation, dependent, of course, on the type of equipments S used on the particular stand.

Each bearing 16 of the lower roller of the stand may also be taken to rest upon a so-called load cell 26 supported in any desired way not shown, the output of which is supplied through an amplifier 27 to a relay designated D D D D D and D associated with the respective stands. These load cells may be of any desired type, one of which is illustrated in Letters Patent of the United States No. 2,895,332, Dahle et al.

While I have shown these load cells as supporting the lower bearing, they may be placed anywhere in the stand where they respond to increased pressure due to presence of the strip 8 in the stand, to produce electromotive force sufiicient when amplified to energize and cause operation of the relays D.

Also associated with each of the stands is one of the relays B B B B B and B through which alternating voltage comprising the above-mentioned correction factor is applied at proper times from contacts a and b, alternatively, these contacts riding on respective potentiometers 48 and 52, shown in FIG. 5. This voltage is supplied through respective conductors 32, or 33, and either one or the other of the lower two armatures of each of such relays B to B dependent on the position of the relay armatures, to the transformers T to T associated with the respective stands. This alternating electromotive force is of one phase, or of opposite phase, and of magnitude dependent on the position of the contact a or b on its respective potentiometer.

Contact a is actuated to varying positions upon potentiometer 48 by a servo motor 87 connected to the output of amplistat 11, shown in FIG. 4, in accord with variations in thickness of the strip being rolled. This adjustment takes place during the interval, hereinafter called the integration interval, when all stands are occupied by the strip and the position of the contact a at the end of that interval corresponds to the integrated thickness of the strip during that interval.

Similarly, contact b is actuated to varying positions along potentiometer 52 by motor 87' connected to the output of amplistat 12 in accord with the thickness of the strip last previously rolled. Contact b, after each integrating interval, is actuated to the position corresponding to the position of contact a at the end of that interval and thus comprises a storage, or memory, of the integrated thickness of the strip last previously rolled.

Both of these potentiometers are connected across the same alternating current source designated AC on the drawing, the frequency of which is the same as that employed in the above-mentioned continuous, or programmed control systems, represented by rectangles S and have desired phase relation thereto.

After each integration interval, as the strip moves to the right out of the mill, relays B to B become deenergized in succession thereby connecting the respective transformers in succession to the contact a, thereby applying the correction factor electromotive force corresponding to the integrated thickness of the strip just rolled to the corresponding transformer, thereby causing the respective screwdown control equipment S to adjust the screwdown for corrected thickness of the next strip. At the beginning of the integration interval of the next strip the relays B to B become energized thereby connecting the corresponding transformers to the contact b which now occupies a position corresponding to the position of contact a at the end of the last integration interval, thereby maintaining the supply of the correction factor voltage to the transformer T during the rolling of the next strip.

As illustrated in FIGS. 1, 2 and 3, the mill stands are all occupied by a strip of steel 8 which extends through all the stands and which travels in the direction of the arrows. This strip, as it enters the mill, may have a thickness in the neighborhood of an inch. As it leaves the mill it may have the thickness of a hundredth of an inch, the thickness having been diminished in each of the stands by the rolling action of the stands to an extent dependent on the pressure applied by the screwdowns.

This rolling action, of course, increases the length of the strip many times as, for example, from feet as it enters the mill to 1800 feet as it leaves the mill.

To gauge the thickness of the strip as it leaves the mill, any desired form of thickness gauge may be employed. For simplicity, I have conventionally illustrated such a thickness gauge by the rectangles 34, 35, 36 and 37. Rectangle 34 may be taken to represent a source of X-rays which projects an X-ray beam through the strip 8 as it leaves the mill to an X-ray detector 35. It also projects a similar beam through an X-ray absorber 38 of predetermined and variable thickness to a second detector 36. The outnputs from these two detectors are supplied in balanced relation to a servo mechanism 37, which controls the position of contact member 39 upon a rheostat 82 across which is connected a source of the unidirectional potential. The arrangementis such that if the strip 8 is of proper thickness, as preset by absorber 38, the output from the detector balances that from detector 36 and the servo motor positions the contact 35? at the midpoint on the potentiometer 82, which point may be considered to be at ground potential. If the strip 8 is too thick, then the servo system operates the contact 39 in one direction, and if it is too thin it operates it in the oppositeidirection. Systems adaptable for this apparatus are shown in Patents 2,7 23,350-Clapp,'2,83 1,980 Howell, and 2,467,812 Clapp. t s

An error, or correction, voltage having one polarity or the other and of magnitude dependent on the direction and extent of thickness deviation from desired value, is supplied during the integration interval, from this contact 39 through conductor 41, potentiometer 83, armature 3 of relay C when energized, conductor 42 and resistance 43 to an operational amplifier 85 across which is connected a condenser 44, whereby this voltage is integrated over the desired interval and the integral voltage is supplied to a potentiometer 45. V

A portion of the integrated potential of potentiometer 45 appears on contact 46, which is operated downward at uniform rate, over resistance 45 by motor 26 during the integration interval. This voltage is utilized to control the position of contacts a and a; and b and 12 upon associated potentiometers 47, 48; and 49, 52. The contacts a and a are driven by servo motor 87 to positions corresponding to the integrated voltage on contact 46 at the end of the integration interval, and the potential on contact a is utilized at the end of that interval to supply the correction factor voltage through conductor 32 and the lower contacts of the various B relays and transformers T to T to the various equipments S to S The contacts b and b are thereafter positioned by motor 87' to agree with the position of a whereby contact 12 supplies the correction factor voltage through the B relays to transformers T to T during the rolling of the next strip.

Contact 46, like contacts a, a; b, b, are carried by a member 54 which rides a screw threaded rod 53 which is driven by the respective motor. Normally, this contact 46 is in its upper position in which a member 86 engages the armature of a limit switch 51 having contacts d, e and 7. In so doing it closes contact d and opens circuits at contacts e and 1. When the contact 46 is operated downward, it opens contacts d and closes contacts e and f.

In addition to the various relays D and B, four relays, C, X, Y and Z, are shown in FIG. 3 of which relay C is quick acting both on energization and deenergization, relay X operates with delay upon energization, and relays Y and Z operate with delay on deenergization.

Power for operation of all of the relays is derived from a suitable power source indicated at the left of FIG. 1 by conductors designated, respectively, +250 v. and 250 v., which conductors are further indicated by heavy lines extending through FIGS. 1, 2 and 3.

All stands occupied by strip being rolled If we assume that all stands of the mill have been occupied by the strip 8 for several seconds, then all relays are in the positions illustrated.

Relays D D D D D and D are energized in response to their respective load cells 26, closing a circuit extending from the positive terminal of the 250 volt source through the middle contacts of relay D and upper contacts of relays D D D D and D conductor 55 and winding of relay X shown in FIG. 3, to the other side of the source. This relay X is energized and, by its lower armature, after a delay of about two seconds, deenergizes relay Y through an obvious circuit. Relay Y in turn by its upper armature deenergizes relay Z through an obvious circuit. Relays Y and Z complete an actuating circuit of relay C, which extends from minus 250 volt armature it completes a holding circuit for itself through conductor 58 and upper armature of relay D to the positive terminal of the source. i

The energization of relay C completes a circuit for the lower winding 59 of motor '26, which extends from ground through that winding, conductor 84, and armature 2 of relay C in its upper position, to the positive terminal of the 250 volt source. Thus, when all of the stands bejtiometer 45 at a constant rate.

, gins.

come occupied by the strip, the motor 26 becomes energized and operates contact 46 downward on the poten- When it leaves its upper position contacts e and f of limit switch 51 close and contacts 0! open. During this time the circuit of the upper winding 66 of motor 20 is maintained open by contact f of the limit switch 51 which is in its open position.

The disengagement of armature d of the limit switch from its contact opens the initial energization circuit of relay C. The relay remains energized by reason of its holding circuit.

The closing of contact e of the limit switch 51 when motor 20 is energized completes a holding circuit for all of the B relays, all of which first became energized through the lower contacts of relay Z in its lower position. This initial energizing circuit extends from the +250 volt source through the lower contacts of relay Z, conductor 52 and the windings of all the B relays in parallel to the negative terminal of the source. These relays are all energized and complete holding circuits for themselves through the lower contacts of the associated D relay, conductor 63 and armature e of the limit switch. 7 It should be noticed at this point that the B relays and relay C do not become energized until the X relay be-- comes energized and the Z relay deenergized, and that this occurs only after all the stands are occupied by the strip. That is, as the strip enters the stands in succession the relays D to .D energize in succession but no further action occurs until all relays D are energized. So long as any stand is unoccupied relay X cannot become energized.

Thus when all the stands are occupied and relay C be comes energized, the integration of the strip thickness be- Contact 46 moves downward on potentiometer 45 at a uniform rate. The resistance element of this potentiometer is so proportioned that the resistance between contact 46 and ground at any point in its downward movement, after the first second of travel, decreases directly as the direct inverse of the total elapsed seconds.

As an example, the following proportions would serve a for a potentiometer designed for a maximum of 64 seconds travel.

Elapsed time, Resistance, 46 to seconds: ground, OHMS O 64 In effect, the error voltage, integrated over the integra tion interval, appears on condenser 44 and on potentiometer 45 and is divided by the duration of the integration.

7 the integration interval, corresponds to and represents the average thickness of that portion of the strip which simultaneously occupies all stands.

After energization of relay X and deenergization of relay Z, i.e., during the integration interval, the voltage on contact 46 is supplied to amplistat 11 through conductor 65, armature 2 of relay X, conductor 66, armature 2 of relay Z, conductor 67, control windings of amplistat 11 to contact a on potentiometer 47. The current supplied through this circuit causes the amplistat 11 to supply to the motor 87 direct current of suitable magnitude and polarity to operate the contact a to a position on resistance 47 corresponding to the voltage on contact 46 of potentiometer 45.

The potential on condenser 44 and potentiometer 45 is, of course, determined by the thickness of the strip as measured by the X-ray thickness gauge 34, 35, 36, 37 and 39, and represents the integration of that thickness over the period when all stands are occupied. The potential on contact 46 is not only dependent upon the integrated voltage on resistance 45 but also upon the position of that contact on resistance 45. The potential across resistance 45 builds up during the integrating interval which begins one second after the strip first occupies all of the stands, i.e., one second after its foremost point enters stand 6 causing relay X to be energized and it continues until the tail end of the strip leaves stand 1 causing relay D and, consequently, relay X to be deenergized. The extent of this build-up is, of course, dependent upon the thickness of the strip. If the strip is too thick the voltage of the upper terminal of resistance 45 may be positive, and if it is too thin it may be 'negative, determined by the position of contact 39 of the X-ray gauge upon its potentiometer 82. Thus the direction and magnitude of the current supplied to the amplistat 11, and which, of course, controls the direction and magnitude of current in the motor 87, varies properly 'to cause the motor to drive contact a to a point on potentiometer 47 corresponding to the voltage on contact 46, thereby reducing the current in the control winding of amplistat 11 to zero whereupon motor 87 stops. One amplistat circuit adapted for use as amplistat 11 is illustrated in FIG. 9 of General Electric publication GER 219, entitled A Self-saturating Static Magnetic Amplifier for Regulating Circuits, published 1952. It is also shown at pages 435 and 436 of the book Magnetic Amplifiers by Storm, published by John Wiley & Sons.

Thus at the end of the integrating interval contacts a and a, stand at a point on their respective potentiometers dependent upon the thickness of the strip. As previously stated, during this interval contact b on potentiometer 52 is connected through conductor 33 and the middle contacts of all of relays B to the respective transformer T to T and supplies corrective voltage of phase and magnitude determined by the thickness of the last strip previously rolled. This maintains voltage supplied to the transformers T to T during the rolling of the strip at substantially the value to which it was adjusted after the rolling of the last previous strip.

Strip leaves the mill When the tail end of strip 8 leaves stand 1 relay D deenergizes. By its upper armature it interrupts -a holding circuit for relay C and by its middle armature it deenergizes relay X. By its lower armature it breaks the holding circuit for relay B Relay X deenergizes which immediately energizes the relay Y which, in turn, immediately energizes relay Z. Relay Z, by its lower armature, interrupts the initial energizat-ion circuit of relay B whereupon relay B deenergiz-es and transfers the connection of transformer T from contact b of potentiometer 52 to contact a of potentiometer 48, thereby to correct the position of the screwdowns of stand 1. Relays X and Z also, by their arma- 8 t-ures 2, disconnect amplistat '11 from contact 46 on potentiometer 45 thereby stopping motor 87.

Relay Z, by its armature 3, deenergizes relay C. Relay C, by its armature 3, disconnects the deviation signal potentiometer 82 from the integrating amplifier 85 and terminates the integrating interval.

After an interval of approximately three seconds the strip leaves stand 2. This causes deenergization of relay D and consequently B thereby transferring the connection of transformer T from potentiometer 52 to potentiometer 48 causing the 'screwdowns of stand 2 to be adjusted to the thickness of the last strip.

This operation is repeated at each successive stand until all of the stands are adjusted Ito-correct for the deviation in the thickness of the strip just rolled from a desired thickness. 7

If no further strip enters the mill until after the first strip has left the mill, then all relays D and B, and relays C and X, become deenergized. Relays Y and Z remain energized, motor 20 remains deenergized and contact 46 remains at the lowermost position to which it was actuated during the integrating interval.

Following strip enters mill before leading strip passes all stands of the mill The time required for the tail end of a leading strip to traverse the mill is greater than the normal interval between strips. Accordingly, a following strip may normally enter the mill while a leading strip is still in some of the stands of the mill. In fact, the interval between the time when any strip leaves a particular stand until a following strip enters that stand may be as short as two seconds. However, it will be noticed that the integration interval of a leading strip terminates when the tail end of that strip leaves stand 1 and the integration interval of the following st-rip begins when the leading end of the following strip enters stand 6. That is, as the following strip enters the successive stands, the D relays operate but no further relay action takes place until the strip occupies all stands.

Thus the lead end and the tail end, each of length equal to the distance between stand 1 and stand 6, are not included in the integration interval, i.e., the thickness of these portions do not affect the adjustment of the screwdowns. This is desired since these portions of the strip are not subject to tensile forces that the intermediate portions may be subjected to by desired operation of the stands and the drives therefor. Thus the thickness of those portions are not true criteria for control of the thickness of the rest of the strip.

When the lead end of the following strip enters stand 6 relay X, which was deenergized when the leading strip left stand 1, again energizes and operates its arma-tures to their upper position after a time delay of about two seconds. This deenergizes relay Y, which operates its armatures to the lower position after a time delay which may be one to six seconds. This deenergizes relay Z which drops its armatures after further delay.

A circuit for amplistat 12 is now completed, which extends from contact b on potentiometer 49 through the control windings of an1plistat'12, conductor 76, lower armature of relay Y, which is closed since it operates to its lower position with time delay, armature 4 of relay X, which closes before the lower armature of relay Y opens, and conductor 89 to contact a on potentiometer 47. This circuit is closed only for an interval after the armatures of relay X attain their upper position and before the armature of relay Y leave-s its upper position. Thus current flows in the control windings of amplistat 12 of intensity and polarity corresponding to the disagreement, if any, between contacts a and b on their respective potentiometers. The amplistat 12, which may be of the same structure as amplistat 11, causes current of amplified intensity and corresponding polarity to flow in motor 49' which operates to move contact b to a position agreeing with that of contact a. When the lower armature of relay Y leaves its upper position the control circuit of amplistat '12 is interrupted.

The closing of the lower contacts of relay Z energizes all of the B relays, thereby transferring the control of all transformers T to potentiometer 52. Relay Z, by its armature 2, also connects amplistat 11 to contact 46 on potentiometer 45 through armature 2 of relay X, in preparation for the next integration interval.

Relay Z also completes a short circuit across condenser 44 of the integrating amplifier 8 to reduce its output to zero. This short circuit extends from the right-hand terminal of condenser 44, through conductor 77, upper arma ture of relay Z, conductor 78, upper armature of relay X, lower armature of relay C, and conductor 79 to the lefthand terminal of condenser 44.

Relay Z also energizes the winding 60 of motor 20 to cause it to operate contact 46 to its top position. This circuit extends from ground through winding 6%, conductor 80, armature 4 of relay Z, armature 3 of relay Y, armature 3 of relay X, conductor 81, and contacts of the limit switch S1. By proper choice of applied volt-age and motor construction, the return of contact 46 to its top position may be eiiected in a very short interval. Contacts open when contact 46 reaches its top position thereby deenergizing motor 20. At the same time contact d closes energizing relay C which closes a holding circuit for itself through the upper contacts of relay D Relay C, by its lower contacts, interrupts the short circuit across condenser 44, thereby reconditioning the integrator for operation over the new integration interval. By its armature 3 it reconnects the input conductor 42 of the integrator to the deviation potentiometer 82 to begin integration, and it connects winding 59 of motor 20 through conductor 15 and armature 2 of relay C to the positive source of operating potential, whereupon the motor again drives contact 46 downward over the potentiometer at a uniform rate to develop a voltage thereon of magnitude corresponding to the integrated thickness of the strip during the integration interval.

This operation repeats for each successive strip.

While I have shown a particular embodiment of my invention, it will, of course, be understood that various modifications may be made both in the structure and instru-mentalities employed without departure from the true spirit and scope of my invention, as set forth in the appended claims.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. The combination, for use in a rolling, mill in which strips of material are rolled under pressure in succession to reduce the thickness thereof to a desired dimension, of means to measure any variation in thickness of each strip from said desired dimension as the strip leaves the mill, and means to store said variation during periods between the rolling of successive strips for controlling the pressure applied in rolling each strip in response to said variation in thickness of the last previous strip as determined by said last means thereby to maintain successive strips of more uniform thickness.

2. The combination, for use in a rolling mill comprising a roll stand through which strips of material are passed in succession for rolling to desired thickness under roll pressure applied by said stand, of means to measure the average deviation in the thickness of each strip from a preselected value while passing said stand and to produce a quantity representing said average deviation in thickness, and means responsive to said quantity to control the pressure applied by said stand to the next strip.

3. The combination, for use in a rolling mill comprising a plurality of roll stands through which strips of material are passed-in succession for rolling to a predetermined thickness under pressure applied by said stands, of means to measure the average deviation in thickness of each strip from said predetermined thickness during the interval in which all of said stands are occupied by the respective strip, and means operative during the interval between the rolling of successive strips to adjust said stands to apply pressure controlled by said measured deviation during the rolling of a succeeding strip more accurately to produce said predetermined thickness in said succeeding strip.

4. The combination, for use in a rolling mill comprising a pluralityrof roll stands through which strips of material are passed in succession for rolling to a predetermined thickness under pressure applied by said stands, of means responsive to the thickness of said strips as they leave the last stand to produce a voltage varying in accord with the direction and magnitude of deviation of said thickness from said predetermined thickness, means to integrate said voltage during the interval in the rolling of each strip when the strip occupies all stands and to produce from said integrated voltage a voltage representative of the average thickness deviation of that portion of the strip passing the last stand during that integrating interval, and means operative after each integrating interval to adjust at least one of said stands to apply pressure determined by said last voltage during the rolling of the succeeding strip.

5. The combination, for use in a rolling mill comprising a plurality of roll stands through which strips of material are passed in succession for rolling to a predetermined thickness under pressure applied by said stands, of means responsive to the thickness of said strips as they leave the last stand to produce a voltage varying in accord with the direction and magnitude of deviation of said thickness from said predetetermined thickness, means to integrate said voltage during the interval in the rolling of each strip when the strip occupies all stands and to produce from said integrated voltage a voltage representative of the average thickness deviation of that portion of the strip passing the last stand during that integrating interval, means operative after each integrating interval to adjust at least one of said stands to apply pressure determined by said last voltage during the rolling of the succeeding strip, and means to supply voltage equal to said last voltage to said adjusting means during the next integration interval.

6. The combination, for use in a rolling mill comprising a plurality of roll stands through which strips of material are passed in succession for rolling to a predetermined thickness under pressure applied by said stands, of means operative during a predetermined interval in the rolling of each strip to produce a parameter corresponding to the average thickness deviation of each strip, means to store said parameter, pressure adjusting means on at least one of said stands, means operative upon termination of each interval and before the next strip enters said one stand to adjust said last means to produce pressure upon said next strip determined by said parameter, and means utilizing said stored parameter to assist in maintaining said adjustment during rolling of the next strip.

7. The combination, for use in a rolling mill comprising a plurality of roll stands through which strips of material pass in succession for rolling to a desired dimension under pressure applied by said stands, at least one stand being equipped with voltage operated means for adjusting said pressure, of means to generate a voltage corresponding to the direction and magnitude of deviation of the thickness of strips coming from the last stand of said mill from a desired value, a voltage integrator, means to connect said voltage generating means to said integrator in response to and during the interval of occupancy of all stands by a single strip, means to develop from the integrated output of said integrator a voltage of magnitude representative of the average thickness deviation of the strip leaving the mill during said interval, and means responsive to termination of each said interval to supply, prior to the next such interval, said last volt- I 1 age to said voltage operated means to adjust said stand to apply pressure determined by the average thickness deviation of the previou strip.

8. The combination, for use in a rolling mill comprlsing a plurality of roll stands through which strips of material pass in succession for rolling to a desired dimension under pressure applied by said stands, at least one stand being equipped with voltage operated means for adjusting said pressure, of means to generate a voltage corresponding to the direction and magnitude of deviation of the thickness of strips coming from the last stand of said mill from a desired value, a voltage integrator, means to connect said voltage generating means to said integrator in response to and during the interval of occupancy of all stands by a single strip, means to develop from the integrated output of said integrator a voltage of magnitude representative of the average thickness deviation of the strip leaving the mill during said interval, means responsive to termination of each said interval to supply prior to the next such interval said last voltage to said voltage operated means to adjust said stand to apply pressure determined by the average thickness deviation of the previous strip, means to store said last voltage and means to supply said stored voltage to said voltage operated means during the next succeeding such interval.

9. The combination, for use in a rolling mill comprising a plurality of roll stands through which strips of material pass in succession for rolling to a desired dimension under pressure applied by said stands, at least one stand being equipped with voltage operated means for adjusting said pressure, of means to generate a voltage corresponding to the direction and magnitude of deviation of the thickness of strips coming from the last stand of said mill from a desired value, a voltage integrator, means to connect said voltage generating means to said integrator in response to and during the interval of occupancy of all stands by a single strip, means to develop from the integrated output of said integrator a voltage of magnitude representative of the average thickness deviation of the strip leaving the mill during said interval, means responsive to termination of each said interval to supply, prior to the next such interval, said last voltage to said voltage operated means to adjust said stand to apply pressure determined by the average thickness deviation of the previous strip, means to store said last voltage and to recondition such integrator to integrate voltage produced by said voltage generating means during the next succeeding such interval, and means to supply the stored voltage to said voltage operated means during said next succeeding such interval.

10. The combination, for use in a rolling mill comprising a plurality of stands through which strips of material pass in succession for rolling to a desired thickness under pressure applied by said stands, certain of said stands having means for adjusting said pressure, of means to measure the deviation in thickness of said strips passing the last stand during the interval when all of said stands are occupied by a single strip and to produce a parameter representing the average thickness deviation during said interval, and means responsive to movement of the tail end of each strip'from each of said certain stands in succession to readjust, in the same succession, and before the next strip enters the respective stands, said pressure adjusting means of the different stands, each adjustment being in response to and in accord with said parameter thereby to reduce the thickness deviation in the next strip rolled.

11. The combination, for use in a rolling mill comprising a plurality of stands through which strips of material pass in succession for rolling to a desired thickness under pressure applied by said stands, certain of said stands having means for adjusting said pressure, of means to measure the deviation in thickness of said strips passing the last stand during the interval when all of said stands are occupied by a single strip and to produce a parameter representing the average thickness deviation during said interval, and means responsive to movement of the tail end of each strip from each of said certain stands in succession to readjust, in the same succession, before the next strip enters the respective stands, said pressure adjusting means of the different stands, each adjustment being in response to and in accord with said parameter thereby to reduce the thickness deviation in the next strip rolled, means to store said parameter, and to apply the stored parameter to said pressure adjusting means of all said certain stands during the corresponding interval in the rolling of the next strip.

12. The combination, for use in a rolling mill having a plurality of stands through which strips of material pass in succession for rolling to a desired thickness under pressure applied by said stands, of means responsive to the passage of any stand by the tail end of any strip to adjust the pressure to be applied by the respective stand to the next strip rolled in accord with any deviation from desired thickness of the strip just passed, a positioning device, means responsive to entry of a following strip into all said stands first to position said positioning device to a position corresponding to the pressure adjustment made by said last means, and means thereafter, during the rolling of the following strip, to maintain said adjustment in accord with the position of said positioning device.

13. In combination, a voltage integrator, a potentiometer across the output of said integrator, said potentiometer having a variable contact, means operative during the rolling of a strip of material in a mill stand to supply to said voltage integrator a voltage varying with deviations in thickness of the strip rolled from a desired dimension for integration thereby, and means operative during said rolling of said strip to move said contact from one end of said potentiometer toward the other to a position where at the end of said rolling of said strip the voltage on said contact represents the average deviation in thickness of said strip from desired value.

14. In combination, a voltage integrator, a potentiometer across the output of said integrator, said potentiometer having a variable contact, means operative during the rolling of a strip of material in a mill stand to supply to said voltage integrator a voltage varying with deviations in thickness of the strip rolled from a desired dimension for integration thereby, means operative during said rolling of said strip to move said contact from one end of said potentiometer toward the other to a position where at the end of said rolling of said strip the voltage on said contact represents the average deviation in thickness of said strip from desired value, a pair of positioning devices, means operative after completion of rolling of one strip and before rolling a second strip to position both said positioning devices to a position determined by said voltage on said contact, to adjust the pressure to be applied by said stand to said second strip in accord with the position of one of said positioning devices and to restore said contact to its initial position and the voltage thereon to zero in readiness for rolling said second strip, and means operative during rolling of said second strip to maintain said adjustment in pressure in accord with the position of the other of said positioning devices.

15. In combination, a voltage integrator, a potentiometer across the output of said integrator, said potentiometer having a variable contact, means operative during the rolling of a strip of material in a mill stand to supply to said voltage integrator a voltage varying with deviations in thickness of the strip rolled from a desired dimension for integration thereby, means operative during said rolling of said strip to move said contact from one end of said potentiometer toward the other to a position Where at the end of said rolling of said strip the voltage on said contact represents the average deviation in thickness of said strip from desired value, a pair of positioning devices, means operative after completion of rolling of one strip to position one of said positioning devices in accord with the voltage on said contact and to adjust the pressure to be applied by said stand to the next strip rolled in accord with the position of said one device, means responsive entry of a second strip into said stand to position the other of said positioning devices to a position corresponding to the position of said one device, to restore said contact to its initial position and the voltage thereon to zero in readiness for rolling said second strip, and means operative during rolling of said second strip to maintain said adjustment in pressure in accord with the positioning of said other positioning device.

References Cited by the Examiner UNITED STATES PATENTS 6/54 Hessenberg et al. 80-32 11/60 Mitchell 8035.1 2/61 Wallace et a1 8032 4/62 Gochenour 8035.'1 8/63 Hulls et al. 8056.2 11/63 Kass et al. 803 5.1

FOREIGN PATENTS 4/ 58 Australia.

WILLIAM J. STEPHENSON, Primary Examiner.

LEON PEAR, Examiner. 

1. THE COMBINATION, FOR USE IN A ROLLING MILL IN WHICH STRIPS OF MATERIAL ARE ROLLED UNDER PRESSURE INSUCCESSION TO REDUCE THE THICKNESS THEREOF TO A DESIRED DIMENSION, OF MEANS TO MEASURE ANY VARIATION IN THICKNESS OF EACH STRIP FROM SAID DESIRED DIMENSION AS THE STRIP LEAVES THE MILL, AND MEANS TO STORE SAID VARIATION DURING PERIODS BETWEEN THE ROLLING OF SUCCESSIVE STRIPS FOR CONTROLLING THE PRESSURE APPLIED IN ROLLING EACH STRIP IN RESPONSE TO SAID VARIATION IN THICKNESS OF THE LAST PREVIOUS STRIP AS DETERMINED BY SAID LAST MEANS THEREBY TO MAINTAIN SUCCESSIVE STRIPS OF MORE UNIFORM THICKNESS. 